Prism Shape Playmat Tube Holder

I bought generic prism playmat holders from amazon and wanted to mount them under a shelf and didn't see any other options out there. The holders i bought were 2.4in (6.1cm) wide by 15" (38cm) long and they slide in with room to spare. Link to playmat holders below. May need to be slightly enlarged/reduced based on brand. I printed with supports auto generated with an overhang threshold of 27degrees to go on from the bed to the bottom of the loop.

Playmat holders i used (no affiliate link) https://www.amazon.com/dp/B0BZYT3HRW